This invention is related to a polymeric coating composition of general utility in, for example, appliance or automotive finishes and coil coatings. More particularly, the coating composition is useful as a top-coat over printed substrates, especially paper, and functions both as an over-print varnish and a barrier coating.
The paper industry utilizes paper chemically treated to fulfill various requirements dictated by the intended use. Paper which is going to be printed requires a coating prior to the printing process to prevent the absorption and spreading of the ink by wicking. The printed paper requires a protective top-coat to minimize the abrasive removal of the printing ink from the surface during the stacking, shipping, and utilization, for example, in packaging.
Common to the top-coatings of the prior art is the inclusion of wax to act as slip agent. The wax migrates to the surface of the coating and the smooth, waxy surface facilitates the rapid movement of the paper and/or packages on the assembly lines. Since the wax is not bound to the coating composition there is a tendency for the wax to be removed or abraded away. The wax also often lowers the gloss of and imparts a blush or haze to the coating thereby down-grading its appearance. In many cases waxes can not be used because of incompatibility with the solvent systems needed for the binder.
The coating composition of this invention has, as one of its components, an ingredient which performs a dual role, that of catalyst and that of slip agent. In this manner the need for the use of the wax is eliminated.